Are you packaging any JBoss specific jar (especially the one that contains that class) within your application deployment? If yes, remove it from your deployment (you can still have it as a compile time dependency if you want to).
By the way, why are you trying to cast it to a specific connection implementation class?
Yes I am using the jboss specific jar "ironjacamar-jdbc-1.0.9.Final.jar" which have the class.
Actually I am using AS400 so I need to typecast the connection to AS400 specific connection